Mufflers for inboard motor boats



June 8, 1965 M. I... PARKER MUFFLERS FOR INBOARD MOTOR BOATS Filed March 27, 1963 R m M 2 JR WW m M M L N 5 T 1 W M l W M Vw, Z i m C. f/ fi United States Patent Filed Mar. 27, 1963, Ser. No. 268,349 17 Claims. (Cl. 131-52) This'invention relates to mufflers and, more particularly, to devices for mufiiing the sound and disposing of exhaust fumes from inboard engines of motor boats.

One of the principal purposes of a mufiler is to reduce the noise of the engine exhaust gases discharging into the atmosphere. An additional problem is encountered with the exhaust of inboard engines of motor boats, since it is common practice to cool inboard engines of motor boats by drawing in sea water and discharging the water along with the exhaust gases in the exhaust outlet, after the water has cooled the engine. The exhaust outlet and the engine muffler therefore, must be capable of handling 'both vapors and liquids and must be particularly resistant to salt water, oil and acids.

Attempts have been made to provide mufflers for inboard engines of motor boats which, although they may effectively reduce the noise level, have been unsuccessful because they often create excessive back pressure in the exhaust line. It has been found that excessive exhaust back pressure causes burning of the valves of the engine and cannot be tolerated.

The transom of a conventional motor boat is substantially upright. As the boat moves through the water, the air currents induced by the motion of the boat form eddy currents around the transom. The exhaust outlet customarily extends through the trans-om, so that when the boat is moving, exhaust gases are caught up in the eddy currents and often flow back over the top of the transom to cause discomfort to passengers on the deck of the boat.

Accordingly, in view of the defects of prior art motor boat mufilers, it is an object of this invention to provide an improved muffler for inboard engines of motor boats.

It is a further object of this invention to provide an exhaust mufiler for inboard engine motor boats which effectively disposes of offensive exhaust fumes.

It is a still further object of this invention to provide a motor boat mufiier which is capable of disposing of water along with the exhaust fumes.

It is another object of this invention to provide an exhaust muffler for inboard engines of motor boats which effectively reduces exhaust noise without creating excessive back pressure in the exhaust pipe.

Thee objects are accomplished in accordance with the preferred embodiment of the invention by a casing which is secured by a flange thereon to the transom of the motor boat, so that it encloses the exhaust outlet. The casing has four side walls. On the interior of the casing, two of the opposite side walls are semicircular and the remaining two opposite side walls have plane surfaces. The casing also is provided with an end wall on the end opposite the flange. The end wall has transverse slots therein adjacent one of the plane side walls. Longitudinal ribs are provided on the plane side walls in the interior of the casing and the ribs extend from the flanged end of'the casing to the end wall. A transverse rib is also provided on the interior of the end wall adjacent the transverse slots. The ribs are triangular in cross-section. Gases from the exhaust outlet flow outward through the slots in the end wall.

This preferred embodiment of the invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a perspective view of a transom of a motor boat with the mufiier of this invention attached thereto;

FIG. 2 is a cross-sectional view of the muffler of this invention along the line 2-2 in FIG. 3

FIG. 3 is a cross-sectional view of the muffler along the line 3-3 in FIG. 4; and

FIG. 4 is a cross-sectional view of the muffler along the line 44 in FIG. 2.

Referring to the drawings, the exhaust outlet pipe 2 from the inboard engine of a motor boat extends through the transom 4 of the boat above the water line 6. The mufiier 8 of this invention is fastened to the transom 4, over the exhaust outlet pipe 2, by means of screws 10, which extend through a flange 12 formed at one end of the muffler 3. The muffler 8 is enclosed by a side wall having opposite semicircular side wall portions 14 and opposite side wall portions 16, the interior walls of which are plane surfaces.

A pair of ribs 18 are formed on the interior surface of each of the plane side wall portions 16 and are equally spaced from the intersection of the plane side wall portions 16 and the semicircular side wall portions 14. A rib 18 on one opposite plane side wall portion 16 is therefore positioned directly opposite a corresponding rib 18 on the opposite plane side wall portion 16.

An end wall 20 encloses the end of the muffler 8 opposite the flange 12. The end wall 20 has formed therein transverse slots 22 which extend substantially parallel to the plane side wall portions 16. The slots 22 are subtantially in axial alignment. As shown in FIGS. 1 and 3, the slots 22 are adjacent the plane side wall portion 16 which is closest to the water line 6 on the transom 4. Furthermore, the slots 22 are in the form of converging nozzles. A transverse rib 24 is formed in the end wall 20 directly above the slots 22.

The position of the muffler 8 relative to the exhaust outlet pipe 2 must be accurately located to obtain the maximum benefit of the muffler. The conventional exhaust outlet is a single pipe 2 which extends approximately one diameter beyond the transom 4. The mutlier S is centered over the outlet pipe, so that the pipe is immediately adjacent the upper plane side wall portion 16 and between the ribs 13. The exhaust gases are then directed against the end wall 29 and expand in opposite directions against the semicircular side wall portions 14. Since the slots 22 are relatively large, the exhaust gases readily flow through the nozzle openings of the slots 22 and are directed rearward of the transom immediately above the water. The slots 22 distribute the exhaust fumes laterally to accomplish maximum mixing with atmospheric air, but at the same time there is sufficient compression as the fumes pass through the slots to direct the fumes rearwardly a sufficient distance to the rear of the boat at the water level to avoid the backwash of air that usually accumulates behind a moving boat.

The mufiier 8 is preferably molded of a resilient elastomer which is capable of retaining its shape, and is resistant to heat, acid, sea water and oil deterioration. One suitable elastomer is neoprene. The ribs 18 and 24 not only direct the flow of exhaust gases within the mufiler 8, but also direct the sound waves in diverging patterns transversely of the slots 22, so that a majority of the sound is absorbed by the side Walls of the mufiler as the sound waves travel a lengthy path before emerging through the slots 22. The transverse slots 22 are sufliciently close to the bottom of the muflier, so that any accumulation of water in the mufiler will be drawn out with the exhaust gases as they flow through the slots 22. A sump 26, as shown in FIG. 3, is provided in the bottom of the mufller below the level of the slots 22 for collecting water.

Some boats have dual exhaust systems in which two exhaust outlet pipes extend side by side through the transom and are spaced apart approximately one diameter or haust pipes then are positioned adjacent the opposite semicircular side wall portions 14. Exhaust gases from the dual pipes follow separate paths along the ribs 1% and are deflected by the end wall 20 in the same manner as with a single exhaust pipe. The principle of operation is substantially the same whether one or two exhaust outlet pipes are served by a single muffler.

As the boat planes through the water, the bow of the boat is relatively higher than the stern and, since the muifler extends beyond the transom, the slots 22 are positioned adjacent the water level of the wake behind the boat. Therefore, the induced draft created by the movement of the water relative to the slots, causes the exhaust fumes to flow out of the slots 22 in a non-diffusing pattern directly above the water. At the water level, the eddy currents are not sufficiently forceful to carry the fumes back over the transom. Accordingly, the muflier of this invention not only reduces the exhaust noise, but also prevents offensive exhaust fumes from reaching the rear deck of the boat.

While this invention has been illustrated and described in one embodiment, it is recognized that modifications and changes may be made therein without departing from the invention as set forth in the claims.

I claim:

1. A mufiler for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, an end wall extending across one end, said end wall having a transverse slot therethrough, said side wall being curved and having centers of curvature substantially in the middle of the casing, but spaced apart transversely of the casing, said casing and said end wall being formed of an elastic and sound absorbing material, ribs extending longitudinally along the side wall in the casing, and means for securing the opposite end of the casing to the transom over the exhaust pipe.

2. A mufller for an inboard motor boat of the type having an exhaust pipe extending through the transom above the Water line comprising a hollow casing having a side wall and opposite ends, an end wall extending across one end, said end wall having a transverse slot therethrough, said side wall being curved and having centers of curvature substantially in the middle of the casing, but spaced apart transversely of the casing, said casing and said end wall being formed of an elastic and sound absorbing material, a pair of ribs on opposite portions of the side wall extending longitudinally along the side wall in the casing, and means for securing the opposite end of the casing to the transom over the exhaust pipe.

3. A muffler for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side Wall and opposite ends, said casing having an end wall extending across one end, said end wall having a transverse slot therethrough, said side wall having opposite semicylindrical portions connected between their longitudinal edges by opposite plane portions to form a continuous side wall, said casing being formed of an elastic and sound absorbing material, a pair of ribs on opposite plane side wall portions extending longitudinally along the side walls in the casing, a transverse rib on the end wall extending along the'slot, and means for securing the opposite end to the transom over the exhaust pipe.

4. An exhaust muliier and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, said side wall having oppositely facing curved interior portions and oppositely facing plane interior portions, an end wall closing one end of the casing, said end wall having a transverse slot, said slot extending substantially parallel to one of said plane interior portions and being offset from the center of said end wall, and means for securing the casing to a transom over the exhaust pipe, whereby the muffler may be centrally mounted over an exhaust pipe with the slot positioned horizontally and below the level of the exhaust pipe for providing effective disposal of exhaust gases and mufliing of exhaust noise.

. 5'. An exhaust muffler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, said side wall having oppositely facing curved interior portions and oppositely facing plane interior portions, a rib in the casing extending along the side wall at each junction of the plane portions and curved portions, an end wall closing one end of the casing, said end Wall having a transverse slot, and means for securing the casing to a transom over the exhaust pipe.

6. An exhaust mufiler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, said side wall having oppositely facing curved portions and oppositely facing plane portions, a rib in the easing extending along the side Wall at each junction of the plane portions and curved portions, an end wall closing one end of the casing, said end wall having first and second elongated slots therein, said slots being in substantially axial alignment and being adjacent one edge of the end wall and means securing the casing to the transom over the exhaust pipe.

7. An exhaust muffler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, said side wall having oppositely facing curved interior portions and oppositely facing plane interior portions, a rib in the casing extending along the side Wall at each junction of the plane portions and curved portions, an end wall closing one end of the casing, a rib in the casing on the end wall adjacent one edge thereof, said end Wall having first and second elongated slots therein, said slots being in substantially axial alignment and being between said end Wall rib and said one edge of said end wall, and means for securing the casing to the transom over the exhaust pipe.

8. An exhaust muffler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, said side wall having oppositely facing curved portions and oppositely facing plane portions, a rib in the casing extending along the side wall at each junction of the plane portions and curved portions, an end wall closing one end of the casing, a rib in the casing on the end wall adjacent one edge thereof, said end wall having first and second elongated slots therein, said slots being in substantially axial alignment and being between said end wall rib and said one edge of said end wall, each of said ribs having sloping sides intersecting to form a pointed edge, said casing and ribs being formed of an elastic and sound absorbing material, and means for securing the casing to the transom with the exhaust pipe extending into the casing adjacent the plane portion of the side wall which is remote from the slots.

9. An engine exhaust muflier comprising a casing, said casing having a side wall and opposite ends, said side wall having four portions secured edge to edge to form a continuous side wall, two of said portions being plane on the interior surface and two of said portions having a semicylindrical interior surface, said plane portions being oppositely facing in the side wall and said semicylindrical surface portions being oppositely facing in the side Wall, an end wall closing one end of the casing, said end wall having an elongated opening therein, said opening extending substantially parallel to one of said plane interior portions and being offset from the center of said end wall and means for securing the opposite end of the casing over an exhaust pipe, whereby the mufller may be centrally mounted over an exhaust pipe with the opening positioned horizontally and below the level of the exhaust pipe for providing effective disposal of exhaust gases and mufiling of exhaust noise.

It). An engine exhaust muffler comprising a casing, said casing having a side wall and opposite ends, said side wall having four portions secured edge to edge to form a continuous side wall, two of said portions being plane on the interior surface and two of said portions having a semicylindrical interior surface, said plane portions being oppositely facing in the side wall and said semicylindrioal surface portions being oppositely facing in the side wall, longitudinal ribs on the interior of the casing between said side wall portions, an end wall closing one end of the casing, a longitudinal rib on the interior of the end Wall extending substantially parallel to a plane side wall portion, said end wall having openings therethrough between said rib and said plane portion and means for securing the opposite end of the casing over an exhaust pipe.

11. An exhaust mufiler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and an end wall extending across one end thereof, said end wall and a portion of said side wall forming a sump in the interior of said casing, said end wall having an elongated slot therein, said slot extending across said end wall and being contiguous with said sump substantially throughout the length of the slot, said slot being spaced intermediate the center of said end wall and the edge of said end wall adjacent said side wall portion, and means for securing the casing to a transom over the exhaust pipe, whereby the muflier may be centrally mounted over an exhaust pipe and the slot is offset from the pipe to deflect exhaust gases to follow a circuitous path and the water in the sump humidifies the exhaust gas as it passes through the slot and makes the gas more dense.

12. An exhaust mufiler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and an end wall extending across one end thereof, said end wall and a portion of said side wall forming a sump in the interior of said casing, said end wall having a plurality of elongated slots therein, said slots being substantially in axial alignment and being contiguous with said sump substantially throughout the length of each slot, said slots being spaced intermediate the center of said end wall and the edge of said end wall adjacent said side wall portion, and means for securing the casing to a transom over the exhaust pipe, whereby the mufiler may be centrally mounted over an exhaust pipe and the slots are offset from the pipe to defiect exhaust gases to follow a circuitous path and the water in the sump humidifies the exhaust gas as it passes through the slot and makes the gas more dense.

13. An exhaust mufiler and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and an end wall extending across one end thereof, said end wall and said side wall forming a sump in the interior of said casing, said end wall having a plurality of elongated slots therein, said slots being substantially in axial alignment and being contiguous with said sump substantially throughout the length of each slot, a rib on the interior of the end wall, said rib extending along the slots on the side opposite the sump, and means for securing the casing to a transom over the exhaust pipe, whereby the Water in the sump humidifies the exhaust gas as it passes through the slot and makes the gas more dense.

14. An exhaust muflier and fume dispersing device for an inboard motor boat of the type having an exhaust pipe extending through the transom above the water line comprising a hollow casing having a side wall and opposite ends, said side wall having oppositely facing curved interior portions and oppositely facing plane interior portions, an end wall closing one end of the casing, said end wall having first and second elongated slots therein, said slots each having one end adjacent one of said curved interior portions and having their opposite end spaced from each other, said slots being in alignment and adjacent one of said plane interior portions, and means for securing the casing to a transom over the exhaust pipe.

15. A muflier according to claim 14 wherein said end wall has an elongated rib on the interior thereof, said slots being between said rib and said one plane interior portion.

16, An engine exhaust mufiler comprising a casing, said casing having a side wall and opposite ends, said side wall having two opposing pairs of side wall portions secured edge to edge to form a continuous side wall, one of said pairs each having a plane interior surface and the other of said pairs each having a semicylindrical interior surface, an end Wall closing one end of the casing, said end wall having first and second elongated slots therein, said slots being in alignment and each having their adjacent ends spaced apart and their remote ends adjacent one of said semicylind-rical side wall portions, and means for securing the casing to a transom over the exhaust pipe.

17. An engine exhaust muffler comprising a casing, said casing having a side wall and opposite ends, said side wall having two opposing pairs of side Wall portions secured edge to edge to form a continuous side wall, one of said pairs each having a plane interior surface and the other of said pairs each having a semicylindrical interior surface, an end wall closing one end of the casing, said end wall having first and second elongated slots therein, said slots each having one end adjacent one of said curved in- .terior portions and having their opposite end spaced from each other, said slots being in alignment and adjacent one of said plane interior portions, and means for securing the casing to the transom with the exhaust pipe extending into the casing adjacent the plane side wall portion which is remote from the slots, said opposite end of each slot being spaced laterally of said exhaust pipe.

References Cited by the Examiner UNITED STATES PATENTS 1,342,464 6/20 S-awders et al 181-57 X 1,395,920 11/21 Libenschek 181-49 2,859,830 11/58 Hoffar 181-47 2, 877,860 3 59 Hotfar.

3,047,091 '7/62 Gerli 181-58 X 3,095,944 7/63 Buxton 181-52 X LEO SMILOW, Primary Examiner. 

1. A MUFFLER FOR AN INBOARD MOTOR BOAT OF THE TYPE HAVING AN EXHAUST PIPE EXTENDING THROUGH THE TRANSOM ABOVE THE WATER LINE COMPRISING A HOLLOW CASING HAVING A SIDE WALL AND OPPOSITE ENDS, AN END WALL EXTENDING ACROSS ONE END, SAID END WALL HAVING A TRANSVERSE SLOT THERETHROUGH, SAID SIDE WALL BEING CURVED AND HAVING CENTERS OF CURVATURE SUBSTANTIALLY IN THE MIDDLE OF THE CASING, BUT SPACED APART TRANSVERSELY OF THE CASING, SAID CASING AND SAID END WALL BEING FORMED OF AN ELASTIC AND SOUND ABSORBING MATERIAL, RIBS EXTENDING LONGITUDINALLY ALONG THE SIDE WALL IN THE CASING, AND MEANS FOR SECURING THE OPPOSITE END OF THE CASING TO THE TRANSOM OVER THE EXHAUST PIPE. 